Organic light-emitting device having a matrix material embedded with heat conducting particles

ABSTRACT

Various embodiments relates to an organic light-emitting device, including at least one functional layer for generating electroluminescent radiation, an encapsulation structure formed on or over the at least one functional layer, and a heat conduction layer formed on or over the encapsulation structure. The heat conduction layer includes a matrix material and heat conducting particles embedded in the matrix material.

RELATED APPLICATIONS

The present application is a national stage entry according to 35 U.S.C.§371 of PCT application No.: PCT/EP2013/050138 filed on Jan. 7, 2013,which claims priority from German application No.: 10 2012 200 485.8filed on Jan. 13, 2012, and is incorporated herein by reference in itsentirety.

TECHNICAL FIELD

Various embodiments relate to an organic light-emitting device and to amethod for processing an organic light-emitting device.

BACKGROUND

An organic light-emitting device, for example an organic light-emittingdiode (OLED), is a luminescent radiator with which electromagneticradiation is generated from electrical energy. An OLED generallyincludes at least one organic functional layer, in which theelectromagnetic radiation is produced. The at least one functional layeris usually arranged between an anode and a cathode. When an on-statepotential is applied, the anode injects holes into the active layer,while the cathode injects electrons. The injected holes and electronsrespectively migrate (under the effect of an externally applied electricfield) to the oppositely charged electrode and, by recombination in thefunctional layer, generate electroluminescent emission.

An OLED has, inter alia, the advantage that it can be used as alarge-surface homogeneous light source. In large-surface OLEDs, however,a significant nonuniform distribution of temperature and luminousdensity often occurs. This is the case, in particular, when busbars arenot used for the current distribution, and when the contacting is on oneside. Owing to the nonuniform distribution, a nonuniform light patternis created with brightness peaks and temperature peaks. These can alsolead to increased ageing of the OLED.

SUMMARY

Various embodiments provide an organic light-emitting device in which aninhomogeneous temperature distribution is reduced or avoided.

Various embodiments provide an organic light-emitting device and amethod for processing an organic light-emitting device.

Various embodiments are described herein in connection with devices, andvarious embodiments are described in connection with methods. Theembodiments and configurations described in connection with the devicesalso apply accordingly, insofar as is expedient, for the methods, andvice versa.

The embodiments and configurations described herein do not necessarilyexclude one another. Rather, one or more embodiments and/orconfigurations may be combined with one another in order to form newembodiments or configurations.

According to various embodiments, a heat conduction layer (in otherwords, a heat conducting or heat distributing layer (also referred to asa thermally conductive layer)) is formed on or over an encapsulation(for example thin-layer encapsulation or encapsulation with glasslamination) of an organic light-emitting device (for example an OLED) inorder to uniformly distribute heat which is generated by a functionallayer or a functional layer stack of the light-emitting device duringoperation of the device, and thereby to achieve a more uniformtemperature distribution and luminous density.

According to one embodiment, an organic light-emitting device includes:at least one functional layer for generating electroluminescentradiation; an encapsulation structure formed on or over the at least onefunctional layer; a heat conduction layer formed on or over theencapsulation structure, the heat conduction layer including a matrixmaterial and heat conducting particles (also referred to as thermallyconductive particles) embedded in the matrix material.

According to another embodiment, a method for processing an organiclight-emitting device includes: provision of an organic light-emittingdevice, which includes at least one functional layer for generatingelectroluminescent radiation and an encapsulation structure formed on orover the at least one functional layer; formation of a heat conductionlayer on or over the encapsulation structure, the heat conduction layerincluding a matrix material and heat conducting particles embedded inthe matrix material.

The terms “arranged on one another”, “formed on one another” and“applied on a layer” as used here mean, for example, that a first layeris arranged immediately in direct mechanical and/or electrical contacton a second layer. A first layer may also be arranged indirectly on asecond layer, in which case further layers may be present between thefirst layer and the second layer.

The terms “arranged over one another”, “formed over one another” and“applied over a layer” as used here mean, for example, that a firstlayer is arranged at least indirectly on a second layer. That is to say,further layers may be present between the first layer and the secondlayer.

In the context of this application, a “functional layer” of the organiclight-emitting device (for example the OLED) is intended to mean a layerwhich is used for charge transport and for light generation in theorganic light-emitting device.

According to one configuration, the at least one functional layer of theorganic light-emitting device is formed as an organic functional layer.

An “organic functional layer” may contain emitter layers, for exampleincluding fluorescent and/or phosphorescent emitters.

The functional layer may be part of a functional layer stack of theorganic light-emitting device, which includes a plurality of functionallayers (for example organic functional layers).

According to various configurations, the organic light-emitting devicemay include a first electrode (for example a cathode) and a secondelectrode (for example an anode), and the functional layer (or thefunctional layer stack) may be formed between the first electrode andthe second electrode.

The term “particles” as used here may mean solid particles whosedimensions (for example diameter) lie in the micrometer range, forexample particles having an average diameter in the range of from a fewmicrometers according to various configurations, for example particleshaving an average diameter in the range of from approximately 1 μm toapproximately 5 μm according to one configuration.

According to another configuration, the heat conducting particlesinclude a material having a high thermal conductivity or consist of amaterial having a high thermal conductivity, for example a materialhaving a thermal conductivity of at least 200 W/(m·K) according to oneconfiguration, for example a material having a thermal conductivity ofat least 500 W/(m·K) according to one configuration.

According to another configuration, the heat conducting particlesinclude at least one metal or consist of at least one metal. Heatconducting particles which consist of at least one metal may also bereferred to as metal particles.

According to another configuration, the heat conducting particlesinclude one or more of the following metals or consist of one or more ofthe following metals: silver, copper, gold, aluminum. Heat conductingparticles which consist of silver may also be referred to as silverparticles. Heat conducting particles which consist of copper may also bereferred to as copper particles. Heat conducting particles which consistof gold may also be referred to as gold particles. Heat conductingparticles which consist of aluminum may also be referred to as aluminumparticles.

According to another configuration, the heat conducting particlesinclude silicon or a conductive silicon compound (for example siliconcarbide). The heat conducting particles may, for example, consist of oneor more of the aforementioned materials. Heat conducting particles whichconsist of silicon may also be referred to as silicon particles. Heatconducting particles which consist of silicon carbide may also bereferred to as silicon carbide particles.

According to another configuration, the heat conducting particlesinclude carbon or a conductive carbon modification (for examplegraphite, diamond, or carbon nanotubes (CNTs)) or carbon compound, orconsist thereof. Heat conducting particles which consist of graphite mayalso be referred to as graphite particles. Heat conducting particleswhich consist of diamond may also be referred to as diamond particles.

According to another configuration, the heat conducting particlesinclude a metal oxide (for example aluminum oxide (Al₂O₃)) and/or ametal salt. The heat conducting particles may, for example, consist ofone or more of the aforementioned materials. Heat conducting particleswhich consist of a metal oxide (for example aluminum oxide) may also bereferred to as metal oxide particles (for example aluminum oxideparticles). Heat conducting particles which consist of a metal salt mayalso be referred to as metal salt particles.

According to other configurations, the heat conducting particles mayinclude other suitable heat conducting materials or consist thereof.

According to another configuration, all the heat conducting particlesinclude the same material or consist thereof.

According to another configuration, the heat conducting particlesinclude different materials or consist of different materials. In otherwords, one part of the heat conducting particles may include a differentmaterial or consist thereof than one or more other parts of the heatconducting particles. Expressed in yet another way, a first part of theheat conducting particles may include a first material or consistthereof and a second part of the heat conducting particles, different tothe first part, may include a second material different to the firstmaterial, or consist thereof.

According to various configurations, the matrix material is different tothe material or materials of the heat conducting particles embeddedtherein.

According to another configuration, the matrix material includes acurable material, for example a thermally curable material or a materialwhich can be cured by means of exposure to light (for example exposureto UV light). As a thermally curing material, for example, a materialmay be used which cures at low temperatures, for example at atemperature in the range of from approximately 50° C. to approximately90° C., for example in the range of from approximately 50° C. toapproximately 80° C. according to one configuration, for example in therange of from approximately 50° C. to approximately 70° C. according toone configuration.

According to another configuration, the matrix material includes anadhesive material or is an adhesive material (also referred to asadhesive or glue), for example an epoxy adhesive, an acrylate adhesive,a silicone adhesive, and/or a thermally and/or UV curing adhesive (forexample thermally and/or UV curing two-component adhesive) (that is tosay an adhesive which can be cured by heating or exposure to UVradiation).

As an alternative or in addition, other suitable adhesive materials maybe used.

According to another configuration, the heat conduction layer is formeddirectly on the encapsulation structure.

According to another configuration, a layer for reducing thereflectivity and/or improving the emissivity is formed on or over theheat conduction layer, for example a nonreflective sheet, for example ablack sheet according to one configuration, or a black (for example mattblack) coating layer according to another configuration, or a blacklayer obtained by anodization according to yet another configuration.

According to another configuration, the layer for reducing thereflectivity and/or improving the emissivity may have a rib pattern.According to an alternative configuration, as an alternative or inaddition to the layer which is used for reducing the reflectivity and/orimproving the emissivity, a layer (for example a sheet) having a ribpattern may be formed on or over the heat conduction layer. The ribs ofthe rib pattern may clearly be used as cooling ribs, in order todissipate the distributed heat to the surroundings.

According to another configuration, as an alternative or in addition toa minimally reflective surface or the use of cooling ribs for the heatdissipation, the applied heat conduction layer or layers or heatdistributing layer or layers may be connected to a housing of theorganic light-emitting device (for example an OLED) or to a heat sink,for example a cooling body.

According to another configuration, the heat conduction layer covers theencapsulation structure over its entire surface. It is, however, alsopossible for the heat conduction layer to cover only a part or parts ofthe encapsulation structure.

According to another configuration, the encapsulation structure isformed as thin-layer encapsulation. As an alternative, the encapsulationstructure may also include glass lamination or be formed as glasslamination.

“Thin-layer encapsulation” (also referred to as “thin-filmencapsulation”) may, for example, mean a layer or a layer structurewhich is suitable for forming a barrier against chemical contaminationor atmospheric substances, in particular against water (moisture) and/oroxygen. In other words, thin-layer encapsulation is formed in such a waythat it cannot be penetrated by atmospheric substances, such as water oroxygen, or can at most be penetrated thereby in very small amounts. Thebarrier effect in the case of thin-layer encapsulation is essentiallyachieved by one or more thin layers which are part of the thin-layerencapsulation. The layer or the individual layers of the thin-layerencapsulation may, for example, have a thickness of less than or equalto a few hundreds of nm.

According to one configuration, the thin-layer encapsulation consists ofthe layer or layers which is or are responsible for the barrier effectof the thin-layer encapsulation. This layer or these layers may also bereferred to as barrier thin layer(s) or barrier thin film(s).

According to another configuration, the thin-layer encapsulation may beformed as a single layer (in other words as one layer).

According to another configuration, the thin-layer encapsulation mayinclude a multiplicity of sublayers formed on one another. In otherwords, according to one configuration the thin-layer encapsulation maybe formed as a layer stack which includes a multiplicity of sublayers(also referred to as barrier thin layers).

The thin-layer encapsulation, or one or more sublayers (barrier thinlayers) of the thin-layer encapsulation may, for example, be formed bymeans of a suitable deposition method, for example by means of an atomiclayer deposition (ALD) method according to one configuration, forexample a plasma enhanced atomic layer deposition (PEALD) method or aplasmaless atomic layer deposition (PLALD) method, or by means of achemical vapor deposition (CVD) method according to anotherconfiguration, for example a plasma enhanced chemical vapor deposition(PECVD) method or a plasmaless chemical vapor disposition (PLCVD)method, or alternatively by means of other suitable deposition methods.

By using an atomic layer deposition (ALD) method, very thin layers canbe deposited. In particular, layers whose layer thicknesses lie in theatomic layer range may be deposited.

According to another configuration, in thin-layer encapsulation whichincludes a plurality of sublayers, all the sublayers may be formed bymeans of an atomic layer deposition method. A layer sequence which onlyincludes ALD layers may also be referred to as a “nanolaminate”.

According to another configuration, in thin-layer encapsulation whichincludes a plurality of sublayers, one or more sublayers of thethin-layer encapsulation may be deposited by a deposition method otherthan an atomic layer deposition method, for example by means of achemical vapor deposition (CVD) method.

According to another configuration, the thin-layer encapsulation mayhave a layer thickness of from approximately 1 nm to approximately 10μm, for example a layer thickness of from approximately 30 nm toapproximately 1 μm according to one configuration, for example a layerthickness of from approximately 300 nm to approximately 600 nm accordingto one configuration, for example approximately 450 nm according to oneconfiguration.

According to another configuration in which the thin-layer encapsulationincludes a plurality of sublayers, all the sublayers may have the samelayer thickness. According to another configuration, the individualsublayers of the thin-layer encapsulation may have different layerthicknesses. In other words, at least one of the sublayers may have adifferent layer thickness than one or more of the other sublayers.

A layer (or sublayer), deposited by means of an atomic layer depositionmethod (ALD method), of the thin-layer encapsulation may, for example,have a layer thickness in the range of from approximately 1 nm toapproximately 1000 nm, for example a layer thickness of fromapproximately 10 nm to approximately 100 nm according to oneconfiguration, for example approximately 50 nm according to oneconfiguration.

A layer (or sublayer), deposited by means of a chemical vapor depositionmethod (CVD method), of the thin-layer encapsulation may, for example,have a layer thickness in the range of from approximately 10 nm toapproximately 10 μm, for example a layer thickness of from approximately30 nm to approximately 1 μm according to one configuration, for examplea layer thickness of from approximately 100 nm to approximately 500 nmaccording to one configuration, for example approximately 400 nmaccording to one configuration.

The layer or the individual sublayers of the thin-layer encapsulationmay respectively include a material which is suitable for protecting thefunctional layer or layers of the organic light-emitting device againstdamaging effects of the surroundings, i.e. for instance against oxygenand/or moisture.

For example, the thin-layer encapsulation or (in the case of a layerstack having a multiplicity of sublayers) one or more of the sublayersof the thin-layer encapsulation may include one of the followingmaterials or consist thereof: an oxide, a nitride or an oxynitride incrystalline or vitreous form. The oxide, nitride or oxynitride may forexample furthermore include aluminum, silicon, tin, zinc, titanium,zirconium, tantalum, niobium or hafnium. The layer or the individualsublayers may for example include silicon oxide (SiO_(x)), for instanceSiO₂, silicon nitride (Si_(x)N_(y)), for instance Si₂N₃, aluminum oxide,for instance Al₂O₃, aluminum nitride, tin oxide, indium tin oxide, zincoxide, aluminum zinc oxide, titanium oxide, zirconium oxide, hafniumoxide or tantalum oxide.

According to another configuration, thin-layer encapsulation whichincludes a plurality of sublayers, all the sublayers may include thesame material or consist thereof. According to another configuration,the individual sublayers of the thin-layer encapsulation may includedifferent materials or consist thereof. In other words, at least one ofthe sublayers may include a different material, or consist thereof, thanone or more of the sublayers other.

According to another configuration, the thin-layer encapsulation may endwith an adhesive layer or a glass lamination. In other words, accordingto one configuration, an adhesive layer or a glass lamination mayoptionally be formed between the thin-layer encapsulation and the heatconduction layer.

According to another configuration, the heat conduction layer has alayer thickness in the range of from approximately 100 μm toapproximately 2 mm according to one configuration, for example a layerthickness in the range of from approximately 200 μm to approximately 500μm according to one configuration. According to other configurations,the layer thickness may have a different value.

According to another configuration, the organic light-emitting devicefurthermore includes at least one additional heat conduction layer,which is formed on or over the heat conduction layer. The at least oneadditional heat conduction layer may be configured in a similar way asthe heat conduction layer, for example according to one or more of theconfigurations described herein in connection with the heat conductionlayer.

The at least one additional heat conduction layer may have a differentmaterial composition (that is to say a different matrix material and/ora different material for heat conducting particles embedded therein)than the heat conduction layer. As an alternative, the at least oneadditional heat conduction layer may have the same material compositionas the heat conduction layer.

The at least one additional heat conduction layer may have a differentlayer thickness than the heat conduction layer (for example beingthicker or thinner than the heat conduction layer). As an alternative,the at least one additional heat conduction layer may have the samelayer thickness as the heat conduction layer.

According to another configuration, the organic light-emitting device isconfigured as an organic light-emitting diode (OLED).

According to another embodiment, an organic light-emitting deviceincludes: at least one functional layer for generatingelectroluminescent radiation; an encapsulation structure formed on orover the at least one active layer; a heat conduction layer formed on orover the encapsulation structure, the heat conduction layer having beenformed by evaporation (also known as thermal evaporation) and/orsputtering (also known as cathode sputtering) and/or plasma deposition(in other words, a plasma enhanced deposition process) and/or spraying(in other words deposition by means of a spray method, for example coldspraying) and/or aerosol deposition of at least one heat conductingmaterial.

According to another embodiment, a method for processing an organiclight-emitting device includes: provision of an organic light-emittingdevice, which includes at least one functional layer for generatingelectroluminescent radiation and an encapsulation structure formed on orover the at least one active layer; formation of a heat conduction layeron or over the encapsulation structure, the heat conduction layer beingformed by means of evaporation and/or sputtering and/or plasmadeposition and/or spraying (in other words, deposition by means of aspray method, for example cold spraying) and/or aerosol deposition of atleast one heat conducting material.

According to one configuration, the at least one heat conductingmaterial includes a material having a high thermal conductivity or is amaterial having a high thermal conductivity, for example a materialhaving a thermal conductivity of at least 200 W/(m·K) according to oneconfiguration, for example a material having a thermal conductivity ofat least 500 W/(m·K) according to one configuration.

According to another configuration, the at least one heat conductingmaterial includes metal or is metal.

According to another configuration, the at least one heat conductingmaterial includes one or more of the following metals or is one of thefollowing metals: silver, copper, gold, aluminum.

According to another configuration, the at least one heat conductingmaterial includes carbon or a conductive carbon modification (forexample graphite of diamond) or carbon compound, or is one of theaforementioned materials.

According to another configuration, the at least one heat conductingmaterial includes silicon or a conductive silicon compound (for examplesilicon carbide) or is one of the aforementioned materials.

According to another configuration, the heat conduction layer is formeddirectly on the encapsulation structure.

According to another configuration, a layer for reducing thereflectivity and/or improving the emissivity is formed on or over theheat conduction layer.

According to another configuration, the layer for reducing thereflectivity and/or improving the emissivity includes a nonreflectivesheet.

According to another configuration, the heat conduction layer covers theencapsulation structure over its entire surface. It is, however, alsopossible for the heat conduction layer to cover only a part or parts ofthe encapsulation structure.

According to another configuration, the encapsulation structure isformed as thin-layer encapsulation. As an alternative, the encapsulationstructure may also include glass lamination or be formed as glasslamination.

According to another configuration, the heat conduction layer has alayer thickness in the range of from approximately 100 μm toapproximately 2 mm, for example a layer thickness in the range of fromapproximately 200 μm to approximately 500 μm according to anotherconfiguration. According to other configurations, the layer thicknessmay have a different value.

According to another configuration, the organic light-emitting devicefurthermore includes at least one additional heat conduction layer,which is formed on or over the heat conduction layer. The at least oneadditional heat conduction layer may be configured in a similar way asthe heat conduction layer, for example according to one or more of theconfigurations described herein in connection with the heat conductionlayer.

The at least one additional heat conduction layer may include adifferent material or consist of a different material than the heatconduction layer. As an alternative, the at least one additional heatconduction layer may include the same material or consist of the samematerial as the heat conduction layer.

The at least one additional heat conduction layer may have a differentlayer thickness than the heat conduction layer (for example beingthicker or thinner than the heat conduction layer). As an alternative,the at least one additional heat conduction layer may have the samelayer thickness as the heat conduction layer.

According to another configuration, the organic light-emitting device isconfigured as an organic light-emitting diode.

According to various embodiments, flat (for example large-surface)organic light-emitting devices (for example large-surface OLEDs) may beprovided, which distribute the heat, which is generated by one or morelight-generating functional layers, uniformly over the surface of theorganic light-emitting device and therefore have a more uniformtemperature distribution. A more uniform temperature distribution canimprove the homogeneity of the light pattern and the lifetime of thedevice (device lifetime). For example, further elements which canfinally dissipate the heat may be attached to the distribution layer.

In conventional designs, the heat has not previously been specificallydistributed. At most, busbars which ensure a more uniform currentdistribution have been resorted to in the design, with the result thatthe temperature distribution is also more homogeneous. Furthermore, carehas been taken to contact the OLED as uniformly as possible and, innon-square or non-round designs, the anode (less conductive) iscontacted on the longer side.

In comparison with OLEDs without a device for temperature distribution,in an organic light-emitting device (for example an OLED) according tovarious embodiments there is homogenization of the temperature and/or animprovement of the luminous density distribution and/or an improvementof the lifetime. Furthermore, by virtue of these improvements, designswhich for example contain fewer busbars, and which are less favorable interms of thermal technology in terms of the connections, are also madeaccessible.

Conventionally, the temperature distribution could also be improved byconventional cooling bodies, although these are much thicker andtherefore counteract the particular thinness and flatness which are anoutstanding feature of OLEDs.

According to some embodiments, a heat conduction layer is applied on anencapsulation structure (for example thin-layer encapsulation, althoughother encapsulations such as for example glass laminations are alsopossible) of an organic light-emitting device (for example an OLED),which uniformly distributes the heat generated during operation byhorizontal thermal conduction. In this way, it is possible to avoidlocal temperature peaks which could otherwise lead to increased ageingat the relevant positions. By virtue of the regularization of thetemperature over the component surface, the luminous density can be atleast partially homogenized, thermally induced differences can becompensated for, and the component can be based on locally isothermalcharacteristics.

According to some embodiments, thermally conductive particles, forexample graphite, carbon nanotubes (CNTs) or metal particles (forexample silver particles) are applied onto an encapsulated organiclight-emitting device, (for example an OLED). Since these particlesgenerally cannot be evaporated, according to various configurations theyare mixed beforehand into a matrix material (for example an adhesive).The layer produced in this way is used for homogenization of the heatdistribution.

In comparison with metal plates or sheets which are applied by means ofa bonding layer (which in the normal case has only a poor thermalconductivity), with the introduction of thermally conductive particlesthe heat can be distributed directly on the encapsulation. Inparticular, in this way it is possible to use carbon nanotubes (CNTs)which have an extremely high thermal conductivity. The heat distributinglayer therefore lies very close to the heat generating layer, and thedistribution can therefore be carried out better than if the heat wasfirst to be transported further outward.

According to some configurations, the heat distributing layer isconfigured in such a way that it is minimally reflective. According tomany configurations, following the application of the heat distributinglayer, a nonreflective layer (for example a nonreflective sheet or thelike) may, for example, additionally be applied.

According to some embodiments, a heat conducting or heat distributinglayer is applied on a thin-film encapsulation of an organiclight-emitting device (for example an OLED) by means of evaporation orsputtering. For example, the layer may also be applied by means of aplasma process, by means of a spray method, for example cold spraying,or by means of an aerosol method (aerosol deposition). The fact that theevaporation or sputtering of the heat conducting layer takes place afterthe application of the thin-film encapsulation has, for example, theadvantage that the organic light-emitting device (for example an OLED)already has a certain degree of protection by the encapsulation, forexample a few hundreds of nm (in principle, an improvement of thethermal conductivity could also be achieved by using a much thickercathode (with a thickness of for example 2 μm instead of 150 nm). This,however, can be carried out only with difficulty in terms of processtechnology: in the case of evaporation with a low evaporation rate, theresidence time during the evaporation would be extremely long, and witha higher rate the OLED would be damaged by excessive heat input duringthe evaporation. Sputtering of the cathode can likewise damage theOLED). Owing to the application of the heat conducting or heatdistributing layer on the thin-layer encapsulation, the heat conductinglayer according to various embodiments lies very close to the heatgenerating layer, and the distribution can therefore take place in animproved way than if the heat was first to be transported furtheroutward. Depending on the material which is used for the heat conductinglayer, evaporation or sputtering may be more suitable, in order, forexample, to apply a correspondingly thick layer as noninvasively aspossible in the shortest possible time.

According to various configurations, the heat conducting layer isconfigured in such a way that it is minimally reflective. According tomany configurations, following the application of the heat conductinglayer, a nonreflective layer (for example a nonreflective sheet or thelike) may, for example, additionally be applied.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like reference characters generally refer to the sameparts throughout the different views. The drawings are not necessarilyto scale, emphasis instead generally being placed upon illustrating theprinciples of the disclosed embodiments. In the following description,various embodiments described with reference to the following drawings,in which:

FIG. 1 shows an organic light-emitting device according to anembodiment;

FIG. 2 shows an organic light-emitting device according to anotherembodiment;

FIG. 3 shows an organic light-emitting device according to anotherembodiment; and

FIG. 4 shows an organic light-emitting device according to anotherembodiment.

DETAILED DESCRIPTION

In the following detailed description, reference is made to the appendeddrawings, which form a part of this description and in which specificembodiments, in which the disclosure can be implemented, are shown forillustration. In this regard, direction terminology such as “up”,“down”, “forward”, “backward”, “front”, “rear”, etc. is used withreference to the orientation of the figure or figures being described.Since components of embodiments can be positioned in a number ofdifferent orientations, the direction terminology is used only forillustration and is in no way restrictive. It is to be understood thatother embodiments may be used and structural or logical modificationsmay be carried out, without departing from the protective scope of thepresent disclosure. It is to be understood that the features of thevarious exemplary embodiments described herein may be combined with oneanother, unless specifically indicated otherwise. The following detaileddescription is therefore not to be interpreted in a restrictive sense,and the protective scope of the present disclosure is defined by theappended claims.

In the scope of this description, terms such as “connected” or “coupled”are used to describe both direct and indirect connection, and direct orindirect coupling.

In the figures, elements which are identical or similar are providedwith identical references, insofar as this is expedient.

FIG. 1 shows an organic light-emitting device 100 according to oneembodiment as a schematic cross-sectional view. The organiclight-emitting device 100 is formed as an OLED. As an alternative, theorganic light-emitting device 100 may be a different organiclight-emitting device.

The organic light-emitting device 100 includes a substrate 101.

The substrate 101 may for example be a transparent support, for examplea glass or a sheet, for example a flexible plastic sheet. As analternative, other suitable substrate materials may be used.

An OLED layer stack 102 is formed on the substrate 101. The OLED layerstack 102 is covered with an encapsulation structure 103 which in theembodiment shown is formed as thin-layer encapsulation. As analternative, other encapsulation structures may also be used, forexample encapsulation with glass lamination.

The OLED layer stack 102 includes one or more sublayers. For example,the OLED layer stack 102 may include a first electrode layer 102 a (forexample an anode layer), which is formed on the substrate 101. The firstelectrode layer 102 a (for example an anode layer) may, for example, beelectrically coupled (not shown) to a first electrode connection (forexample an anode connection). The first electrode layer 102 a (forexample an anode layer) may be transparent and for example include asuitable transparent conductive material, for example a transparentconductive oxide (TCO), for example a transparent metal oxide such as,for example, indium tin oxide (ITO). As an alternative, the firstelectrode layer 102 a (for example an anode layer) may include othersuitable materials.

A functional layer stack including at least one organic functional layer102 b may be applied on the first electrode layer 102 a (for example ananode layer) of the OLED stack 102. A second electrode layer 102 c (forexample a cathode layer) of the OLED stack 102 may be applied over ofthe functional layer stack including the at least one organic functionallayer 102 b. The second electrode layer 102 c (for example a cathodelayer) may, for example, be electrically coupled (not shown) to a secondelectrode connection (for example a cathode connection).

The functional layer stack may include one or a multiplicity of organicfunctional layers 102 b. At least, an active layer, in which emittedradiation is generated as soon as an electrical voltage is applied tothe active layer, may be provided. The active layer may include anelectroluminescent material. For example, the electroluminescentmaterial may include suitable polymers for fluorescence orphosphorescent emission. As an alternative, small organic molecules,which emit by means of fluorescence or phosphorescence, may be used asan active layer (organic electroluminescent layer).

When an on-state potential is applied, the anode injects holes into theanode layer, while the cathode injects electrons into the cathode layer.The injected holes and electrons respectively migrate (under the effectof an externally applied electric field) to the oppositely chargedelectrode and, by recombination in the active layer, generateelectroluminescent emission.

The delivery of the charge carriers may respectively take place via acharge transport layer. A charge transport layer arranged between theanode layer and the active layer is also referred to as a hole transportlayer (HTL). It may, for example, include a p-doped conductive organicor inorganic material. A charge transport layer arranged between thecathode layer and the active layer is also referred to as an electrontransport layer (ETL). It may, for example, include an n-dopedconductive organic or inorganic material. For both charge transportlayers, suitable intrinsic, i.e. undoped layers may also be used. Thecharge transport layers are likewise part of the functional layer stack.

In order to be able to apply an electric voltage to the functional layerstack, or to the active layer, the first electrode layer 102 a (forexample an anode layer) may be connected to the first electrodeconnection (for example an anode connection), and the second electrodelayer 102 c (for example a cathode layer) may be connected to the secondelectrode connection (for example a cathode connection). The first andsecond electrode connections may be connected to an energy source. Forexample, they may be coupled to a constant current source, and forexample a battery or a driver circuit.

The first electrode layer 102 a (for example an anode layer) and thesecond electrode layer 102 c (for example a cathode layer) are used asan electrical feed of charge carriers to the organic functional layer orlayers, which is or are arranged between the cathode and the anode.

During the recombination of charge carriers in the active layer of thefunctional layer stack, and owing to ohmic resistances in the electricalfeeds, heat is produced inside the organic light-emitting device 100.This is particularly detrimental for the materials in the organicfunctional layer or layers 102 b of the OLED layer stack 102. Thematerials used there are generally organic molecules or organicmacromolecules (polymers). These can be degraded by thermal effects, andin particular processes such as dissociation can take place. Thoseorganic materials which are used in the production of an OLED may bemodified by the effect of temperature both in molecular structure and inmaterial structure (for example by (re)crystallization, glasstransitions, etc.), so that different optical properties may be induced,for example in terms of the emission spectra or the refractive index.

In large-surface organic light-emitting devices (for examplelarge-surface OLEDs), a nonuniform distribution of temperature andluminous density may furthermore occur, so that a nonuniform lightpattern can be created with brightness peaks and temperature peaks.

In the embodiment shown, a heat conduction layer 104 is provided, whichis formed on the encapsulation 103 and is used to uniformly distributethe heat produced so that brightness peaks and temperature peaks can beavoided. To this end, the heat conduction layer 104 includes thermallyconductive particles 104 b which are embedded in a matrix material 104a.

The thermally conductive particles 104 b may include a material having ahigh thermal conductivity or consist thereof, for example a materialhaving a thermal conductivity of at least 200 W/(m·K) according to oneconfiguration, for example a material having a thermal conductivity ofat least 500 W/(m·K) according to one configuration.

According to one configuration, for example, the thermally conductiveparticles 104 b include a metal or consist of a metal, for examplesilver, copper, gold or aluminum.

According to another configuration, the thermally conductive particles104 b may, for example, include silicon or consist thereof.

According to another configuration, the heat conducting particles 104 bmay, for example, include silicon carbide or consist thereof.

According to another configuration, the thermally conductive particles104 b may, for example, include a carbon-based material, for examplegraphite, diamond and/or carbon nanotubes (CNTs) or consist thereof.

According to another configuration, the thermally conductive particles104 b may, for example, include a metal oxide, for example aluminumoxide (Al₂O₃), and/or a metal salt.

According to one configuration, the thermally conductive particles 104 bmay all include the same material, or consist thereof. According toanother configuration, the thermally conductive particles 104 b mayinclude different materials or consist of different materials. In otherwords, one part of the thermally conductive particles 104 b may includea different material or consist thereof than one or more other parts ofthe thermally conductive particles 104 b. Expressed in yet another way,a first part of the thermally conductive particles 104 b may include afirst material or consist thereof and a second part of the thermallyconductive particles 104 b, different to the first part, may include asecond material different to the first material, or consist thereof.

The matrix material 104 a may for example be an adhesive, for example anepoxy adhesive, an acrylate adhesive, a silicone adhesive, a thermallyand/or UV curing adhesive (for example a thermally and/or UV curingtwo-component adhesive), or any other suitable adhesive. As analternative, other suitable materials in which the thermally conductiveparticles 104 b can be embedded may be used as a matrix material 104 aof the heat conduction layer 104.

According to one configuration, the organic light-emitting device 100may optionally include a layer 105 for reducing the reflectivity and/orimproving the emissivity, formed on the heat conduction layer 104, asshown in FIG. 1. The layer 105 may for example be a nonreflective sheet,for example a black sheet, or a black (for example matt black) coatinglayer or a black layer obtained by anodization. As an alternative, thelayer 105 may be another suitable layer, which is suitable for reducingthe reflectivity and/or improving the emissivity.

The heat conduction layer 104 may follow on directly from theencapsulation structure 103, as shown. In other words, the heatconduction layer 104 may be applied directly on the encapsulationstructure 103. As an alternative, one or more additional layers (notshown), for example a protective layer according to one configuration,may be formed between the encapsulation structure 103 (for examplethin-layer encapsulation) and the heat conduction layer 104.

According to another configuration, at least one additional heatconduction layer (not shown) may be formed on the heat conduction layer104. The at least one additional heat conduction layer may be configuredin a similar way as the heat conduction layer 104, for example accordingto one or more of the configurations described herein in connection withthe heat conduction layer 104. The layer 105 (if present) may in thiscase be formed on the at least one additional heat conduction layer.Clearly, a layer stack including a multiplicity of heat conductionlayers formed on one another may be applied on the encapsulationstructure 103, and the layer 105 (if present) may be formed on the layerstack.

FIG. 2 shows an organic light-emitting device 200 according to anotherembodiment as a schematic cross-sectional view. The organiclight-emitting device 200 is formed as an OLED. As an alternative, theorganic light-emitting device 200 may be a different organiclight-emitting device.

The organic light-emitting device 200 includes a substrate 201, an OLEDlayer stack 202 formed on the substrate 201 and an encapsulationstructure 203, which is formed on the OLED layer stack 202 and is formedas thin-layer encapsulation (as an alternative, the encapsulationstructure 203 may also be a different encapsulation, for exampleencapsulation with glass lamination).

The substrate 201, the OLED layer stack 202 and the encapsulationstructure or thin-layer encapsulation 203 may, for example, beconfigured according to one or more of the configurations describedherein, for example in a similar way as the substrate 101, the OLEDlayer stack 102 and the encapsulation structure 103, which weredescribed above in connection with FIG. 1.

In the embodiment shown, a heat conduction layer 204 is provided, whichis formed on the encapsulation 203 and is used to uniformly distributethe heat produced so that brightness peaks and temperature peaks can beavoided.

To this end, heat conduction layer 204 includes at least one heatconducting material, or consists of at least one heat conductingmaterial, which can be applied or deposited on the encapsulationstructure 203 by means of evaporation and/or sputtering and/or plasmadeposition and/or spraying and/or aerosol deposition.

The at least one heat conducting material may have a high thermalconductivity, for example a thermal conductivity, for example a materialhaving a thermal conductivity of at least 200 W/(m·K) according to oneconfiguration, for example a thermal conductivity of at least 500W/(m·K) according to another configuration.

As materials with a high thermal conductivity, which can be evaporatedor sputtered, metals may for example be used. In particular, forexample, silver, copper, gold and aluminum have very high thermalconductivities and may therefore be used advantageously as material forthe heat conduction layer 204.

According to one configuration, the heat conduction layer 204 may forexample be an evaporated aluminum layer, for example (but notexclusively) if the encapsulation structure 203 is thin-layerencapsulation which terminates with aluminum. According to anotherconfiguration, the heat conduction layer 204 may be a sputtered aluminumlayer. Particularly good adhesion/connection to thethin-film-encapsulated layer can be obtained by virtue of the sputteredions. In a similar way, according to other configurations, the heatconduction layer 204 may for example be an evaporated or sputteredsilver layer, or an evaporated or sputtered copper layer, or anevaporated or sputtered gold layer.

According to other configurations, as an alternative or in addition,other suitable materials, which have a thermal conductivity that is ashigh as possible and can be applied by means of evaporation orsputtering, may be used for the heat conduction layer 204.

As materials with a high thermal conductivity, which can be applied ordeposited by a plasma process, diamond or silicon carbide may forexample be used. In other words, the heat conduction layer 204 may forexample be formed as a diamond layer or a silicon carbide layer, whichhave respectively been applied by means of a plasma enhanced depositionprocess. According to other configurations, as an alternative or inaddition, other suitable materials, which have a thermal conductivitythat is as high as possible and can be applied by means of plasmadeposition, may be used for the heat conduction layer 204.

According to one configuration, the organic light-emitting device 200may optionally include a layer 205 for reducing the reflectivity and/orimproving the emissivity, formed on the heat conduction layer 204, asshown in FIG. 2. The layer 205 may for example be a nonreflective sheet,for example a black sheet, or a black (for example matt black) coatinglayer or a black layer obtained by anodization. As an alternative, thelayer 205 may be another suitable layer, which is suitable for reducingthe reflectivity and/or improving the emissivity.

The heat conduction layer 204 may follow on directly from theencapsulation structure 203, as shown. In other words, the heatconduction layer 204 may be applied directly on the encapsulationstructure 203. As an alternative, one or more additional layers (notshown), for example a protective layer according to one configuration,may be formed between the encapsulation structure 203 (for examplethin-layer encapsulation) and the heat conduction layer 204.

According to another configuration, at least one additional heatconduction layer may be formed on the heat conduction layer 204, asshown for example in FIG. 3.

FIG. 3 shows an organic light-emitting device 300 according to anotherembodiment as a schematic cross-sectional view. The organiclight-emitting device 300 is formed as an OLED. As an alternative, theorganic light-emitting device 300 may also be a different organiclight-emitting device.

The organic light-emitting device 300 includes a substrate 301, an OLEDlayer stack 302 formed on the substrate 301 and an encapsulationstructure 303, which is formed on the OLED layer stack 302 and is formedas thin-layer encapsulation (as an alternative, the encapsulationstructure 303 may also be a different encapsulation, for exampleencapsulation with glass lamination), and a heat conduction layer 304formed on the encapsulation structure 303.

The substrate 301, the OLED layer stack 302, the encapsulation structureor thin-layer encapsulation 303 and the heat conduction layer 304 may,for example, be configured according to one or more of theconfigurations described herein, for example in a similar way as thesubstrate 201, the OLED layer stack 202, the encapsulation structure 203and the heat conduction layer 204, which were described above inconnection with FIG. 2.

The organic light-emitting device 300 differs from the organiclight-emitting device 200 shown in FIG. 2 in that an additional heatconduction layer 304′ is formed on the heat conduction layer 304. Theadditional heat conduction layer 304′ may, like the heat conductionlayer 304, have been formed by means of evaporation, sputtering orplasma deposition of at least one heat conducting material. As heatconducting materials for the additional heat conduction layer 304′, forexample, one or more materials which may also be used for the heatconduction layer 304 may be used, for example metals with a thermalconductivity which is as high as possible, for example silver, copper,gold, aluminum, or diamond or silicon carbide, or other suitable heatconducting materials which can be applied by evaporation and/orsputtering and/or by plasma deposition and/or spray methods and/oraerosol methods.

According to one configuration, the heat conduction layer 304 may forexample be an evaporated or sputtered aluminum layer and the additionalheat conduction layer 304′ may be a sputtered silver layer. In otherwords, according to this configuration, the heat conduction layer 304may be formed first by means of evaporation or sputtering of aluminum,and the additional heat conduction layer 304′ may subsequently be formedby means of sputtering of silver. Silver can generally be sputtered atfaster rates than it can be evaporated. A thick layer can therefore begenerated more easily, and the thermal conductivity of silver is muchhigher than that of aluminum.

According to another configuration, the heat conduction layer 304 mayfor example be an evaporated or sputtered silver layer, and theadditional heat conduction layer 304′ may be an evaporated or sputteredaluminum layer. In other words, according to this configuration, theheat conduction layer 304 may be formed first by means of evaporation orsputtering of silver, and the additional heat conduction layer 304′ maysubsequently be formed by means of evaporation or sputtering ofaluminum.

According to one configuration, the organic light-emitting device 300may optionally include a layer 305 for reducing the reflectivity and/orimproving the emissivity, formed on the additional heat conduction layer304′, as shown in FIG. 3. The layer 305 may for example be anonreflective sheet, for example a black sheet, or a black (for examplematt black) coating layer, or a black layer obtained by anodization. Asan alternative, the layer 305 may be another suitable layer, which issuitable for reducing the reflectivity and/or improving the emissivity.

FIG. 4 shows an organic light-emitting device 400 according to anotherembodiment as a schematic cross-sectional view. The organiclight-emitting device 400 is formed as an OLED. As an alternative, theorganic light-emitting device 400 may be a different organiclight-emitting device.

The organic light-emitting device 400 includes a substrate 401, an OLEDlayer stack 402 formed on the substrate 401 and an encapsulationstructure 403, which is formed on the OLED layer stack 402 and is formedas thin-layer encapsulation (as an alternative, the encapsulationstructure 403 may also be a different encapsulation, for exampleencapsulation with glass lamination), and a heat conduction layer 404formed on the encapsulation structure 403.

The substrate 401, the OLED layer stack 402, the encapsulation structureor thin-layer encapsulation 403 and the heat conduction layer 404 may,for example, be configured according to one or more of theconfigurations described herein, for example in a similar way as wasdescribed with reference to FIG. 1 to FIG. 3.

The organic light-emitting device 400 furthermore includes a layer 406having a rib pattern, which is formed on the heat conduction layer 404.The rib pattern includes a multiplicity of ribs 406 a. The ribs 406 amay clearly be used as cooling ribs for heat dissipation.

According to another configuration, the layer 406 may be configured as anonreflective layer for reducing the reflectivity and/or improving theemissivity. As an alternative, according to another configuration, anadditional layer for reducing the reflectivity and/or improving theemissivity may be formed between the heat conduction layer 404 and thelayer 406.

LIST OF REFERENCES

-   100, 200, 300, 400 organic light-emitting device-   101, 201, 301, 401 substrate-   102, 102, 302, 402 OLED layer stack-   102 a first electrode layer-   102 b organic functional layer-   102 c second electrode layer-   103, 203, 303, 403 encapsulation structure-   104, 204, 304, 404 heat conduction layer-   104 a matrix material-   104 b heat conducting particles-   105, 205, 305 reflectively-reducing layer-   304′ additional heat conduction layer-   406 rib pattern layer-   406 a rib

The invention claimed is:
 1. An organic light-emitting device,comprising: at least one functional layer for generatingelectroluminescent radiation; a glass encapsulation structure formed onor over the at least one functional layer; and a heat conduction layerformed on or over the glass encapsulation structure, the heat conductionlayer comprising a matrix material and heat conducting particlesembedded in the matrix material.
 2. The organic light-emitting device asclaimed in claim 1, wherein the heat conducting particles comprise amaterial having a thermal conductivity of at least 200 W/(m·K).
 3. Theorganic light-emitting device as claimed in claim 1, wherein the heatconducting particles comprise at least one of a metal; carbon or aconductive carbon modification or carbon compound; silicon or aconductive silicon compound; a metal oxide; and a metal salt.
 4. Theorganic light-emitting device as claimed in claim 1, wherein the heatconductive particles comprise carbon nanotubes.
 5. The organiclight-emitting device as claimed in claim 1, wherein the matrix materialcomprises an adhesive material.
 6. The organic light-emitting device asclaimed in claim 1, wherein the heat conduction layer is formed directlyon the glass encapsulation structure.
 7. The organic light-emittingdevice as claimed in claim 1, further comprising a layer for reducingthe reflectivity and/or improving the emissivity, which is formed on orover the heat conduction layer.
 8. The organic light-emitting device asclaimed in claim 1, wherein the glass encapsulation structure is formedas thin-layer encapsulation.
 9. The organic light-emitting device asclaimed in claim 1, further comprising a layer having a rib pattern,which is formed on or over the heat conduction layer.
 10. The organiclight-emitting device as claimed in claim 1, wherein the heat conductionlayer has a thickness in the range of from approximately 100 μm toapproximately 2 mm.
 11. The organic light-emitting device as claimed inclaim 1, further comprising at least one additional heat conductionlayer, which is formed on or over the heat conduction layer.
 12. Theorganic light-emitting device as claimed in claim 1, wherein the heatconduction layer covers the glass encapsulation structure over itsentire surface.
 13. The organic light-emitting device as claimed inclaim 1, configured as an organic light-emitting diode.